QueenAttack.py

def initialize(n):
    for key in ['queen', 'row', 'col', 'nwtose', 'swtone']:
        board[key] = {}
    for i in range(n):
        board['queen'][i] = -1
        board['row'][i] = 0
        board['col'][i] = 0
    for i in range(-(n - 1), n):
        board['nwtose'][i] = 0
    for i in range(2 * n - 1):
        board['swtone'][i] = 0


def printing(t, n):
    for i in range(n):
        print("----" * n, end="")
        print("-")
        for j in range(n):
            if (i, j) in t:
                print("| {} ".format("Q"), end="")
            else:
                print("|   ", end="")

        print("|")
    print("----" * n, end="")
    print("-")


def printboard():
    print(board)
    li = list()
    for row in sorted(board['queen'].keys()):
        li.append((row, board['queen'][row]))
    printing(li, len(li))


def free(i, j):
    return(board['row'][i] == 0 and board['col'][j] == 0 and
           board['nwtose'][j - i] == 0 and board['swtone'][j + i] == 0)


def addqueen(i, j):
    board['queen'][i] = j
    board['row'][i] = 1
    board['col'][j] = 1
    board['nwtose'][j - i] = 1
    board['swtone'][j + i] = 1


def undoqueen(i, j):
    board['queen'][i] = -1
    board['row'][i] = 0
    board['col'][j] = 0
    board['nwtose'][j - i] = 0
    board['swtone'][j + i] = 0


def placequeen(i):
    n = len(board['queen'].keys())
    for j in range(n):
        if free(i, j):
            addqueen(i, j)
            if i == n - 1:
                return(True)
            else:
                extendsoln = placequeen(i + 1)
            if extendsoln:
                return(True)
            else:
                undoqueen(i, j)
    else:
        return(False)


board = {}
n = int(input("How many queens? "))
initialize(n)
if placequeen(0):
    printboard()